1. Field of the Invention
The present invention relates to a method for estimating quantities that represent the state of a vehicle, such as the vehicle body sideslip angle.
2. Description if the Related Art
Conventionally, a control method is known for improving the maneuverability of a vehicle by using the quantities that represent the vehicle state, such as the vehicle body sideslip angle β (that is, the angle between the forward direction of the vehicle and the longitudinal axis of the vehicle) when controlling the state of movement of the vehicle during a turning movement, for example. In this type of control, a method is known wherein, in the case that, for example, the vehicle body sideslip angle β is used, the yaw rate r detected by a yaw rate sensor (that is, the turn angle speed of the vehicle center of gravity around the axis in the vertical direction), the lateral acceleration Gy detected by the lateral acceleration sensor (that is, the acceleration or deceleration added in the lateral direction of the vehicle), and the velocity V of the vehicle (vehicle speed) detected by the vehicle velocity sensor are substituted into the following equation 1, which is derived from the equation representing the physical relations of the quantities that represent the state of the movement of the vehicle, and by carrying out integration with respect to time, the vehicle body sideslip angle β is estimated.
However, in methods in which the results of the detected quantities from each of the sensors are integrated with respect to time, the influence of noise in each of the sensors, the error included in the results of the detected quantities, and the deviations in the calibrations of each of the sensors accumulate, and thus there is the concern that the precision of the estimation of the vehicle body sideslip angle β the deteriorates.                     β        =                  ∫                                    (                                                                    G                    y                                    V                                -                r                            )                        ⁢                          ⅆ              t                                                          Eq        .                                   ⁢        1            
In response to these problems, the method of estimating the vehicle body sideslip angle and estimating apparatus disclosed, for example, in Japanese Unexamined Patent Application, First Publication, No. Hei 11-78933, is known. In this method, models of a plurality of wheels is introduced, and the vehicle body sideslip angle β is estimated by switching the model for the wheels depending on, for example, the case that the coefficient of friction of the road surface changes or the various conditions during travel in the critical vicinity of movement of the vehicle (that is, the critical zone in which there is the possibility that the state of movement of the vehicle may become unstable when there is no control of any kind).
However, in the vehicle body sideslip angle estimation method and estimation apparatus according to the example of conventional technology described above, there are the problems that the computation processing of the vehicle body sideslip angle β becomes complicated, and that the computation load increases.
Furthermore, there are cases in which the estimated value of the vehicle body sideslip angle β drastically changes due to the timing during which the models of a plurality of wheels is switched, and thus the there is a concern that the drivability will deteriorate.
In consideration of the problems described above, it is an object of the present invention to provide a method of estimating for the quantities representing the state of the vehicle that can improve the precision of the estimations of the vehicle body sideslip angle or values related to the vehicle body sideslip angle by a simple and inexpensive method.